Download File - Home

07/07/2017
P3 Sustainable Energy
(OCR 21st Century)
W Richards
The Weald School
P3.1 How much Energy do we use?
07/07/2017
Energy Consumption
07/07/2017
The demand for energy is predicted to rise by a large amount
in the next few decades:
What issues will this rise in demand cause?
Fuels
07/07/2017
A “fuel” is something that can be burned to release heat and
light energy. The main examples are:
Coal, oil and gas are called “fossil fuels”. In
other words, they were made from fossils.
Some definitions…
07/07/2017
A renewable energy source is clearly one that can be _______
(“renew = make again”), e.g. _____, solar power, biogas etc.
A ___________ energy source is one that when it has been
used it is gone forever. The main examples are ____, oil and
gas (which are called ______ ____, as they are made from
fossils), and nuclear fuel, which is non-renewable but NOT a
fossil fuel.
Electricity is called a “________ source” because it is
converted from other forms – what would these forms be in
batteries, wind turbines and solar panels?
Words – non-renewable, coal, fossil
fuels, wood, renewed, secondary
Pollution
07/07/2017
When a fuel is burned the two main waste products are _____
dioxide and ________ dioxide.
Carbon dioxide is a _________ ___ and helps cause _______
_________. This is produced when any fossil fuels are
burned.
Sulphur dioxide, when dissolved in ________, causes ______
_____. This is mainly a problem for ___ power stations.
Nuclear power stations do not produce these pollutants
because they don’t ____ fossil fuels.
Words – sulphur, coal, global warming, carbon,
acid rain, greenhouse gas, rainwater, burn
Using Electricity
07/07/2017
Basically, electrical devices are used to transfer electrical
energy to the environment:
+
-
This light bulb will transfer
light and heat to the
surroundings.
Energy and Power
07/07/2017
The POWER RATING of an appliance is simply how much
energy it uses every second.
In other words, 1 Watt = 1 Joule per second
E
E = Energy (in joules)
P = Power (in watts)
T = Time (in seconds)
P
T
Some example questions
07/07/2017
1) What is the power rating of a light bulb that transfers
120 joules of energy in 2 seconds?
60W
2) What is the power of an electric fire that transfers
10,000J of energy in 5 seconds?
2KW
3) Rob runs up the stairs in 5 seconds. If he transfers
1,000,000J of energy in this time what is his power
rating?
0.2MW
4) How much energy does a 150W light bulb transfer in a)
one second, b) one minute?
150J,
9KJ
5) Jonny’s brain needs energy supplied to it at a rate of
40W. How much energy does it need during a 50 minute
physics lesson?
120KJ
6) Lloyd’s brain, being more intelligent, only needs energy at
a rate of about 20W. How much energy would his brain
use in a normal day?
630MJ
Power
07/07/2017
Power is “the rate of doing work”.
The amount of power being used in
an electrical circuit is given by:
Power = voltage x current
in W
in V
in A
P
V
I
We can use this equation to analyse power stations:
1) A transformer gives out 10A at a voltage of 50V. What is
its power output?
500W
2) An electric fire has a power rating of 2KW. If it runs on a
voltage of 230V what is the current?
8.7A
3) Electricity is transmitted along some lines in the National
Grid at 400KV. If the current is 1KA what would be the
power through the wire?
400MW
The Cost of Electricity
07/07/2017
Electricity is measured in units called “kilowatt hours” (kWh).
The kilowatt hour is a unit of energy but the Joule is too small
to count so we use the KWh instead. For example…
A 3kW fire left on for 1 hour uses 3kWh of energy
A 1kW toaster left on for 2 hours uses 2kWh
A 0.5kW hoover left on for 4 hours uses __kWh
A 200W TV left on for 5 hours uses __kWh
A 2kW kettle left on for 15 minutes uses __kWh
The Cost of Electricity
07/07/2017
To work out how much a device costs we do the following:
Cost of electricity = Power (kW) x time (h) x cost per kWh (p)
For example, if electricity costs 8p per unit calculate the cost
of the following…
1) A 2kW fire left on for 3 hours
48p
2) A 0.2kW TV left on for 5 hours
8p
3) A 0.1kW light bulb left on for 10 hours
8p
4) A 0.5kW hoover left on for 1 hour
4p
Reading Electricity Meters
07/07/2017
1) How many units of electricity
have been used?
2) If 1 unit costs 10p how much
has this electricity cost?
The 9 types of energy
Type
Heat
Kinetic (movement)
Nuclear
Sound
Light
Chemical
Electrical
Gravitational potential
Elastic potential
3 example sources
07/07/2017
The Laws of Physics
07/07/2017
There are many laws of physics, but one of the most important
ones is:
Energy cannot be created or
destroyed, it can only be converted
from one form to another
Energy changes
07/07/2017
To describe an energy change for a
light bulb we need to do 3 steps:
1) Write down the
starting energy:
2) Draw an arrow
Electricity
3) Write down
what energy types
are given out:
Light + heat
What are the energy changes for the following…?
1) An electric fire
2) A rock about to drop
3) An arrow about to be fired
Conservation of Energy
07/07/2017
In any energy change there is ALWAYS some “waste” energy:
e.g. a light bulb:
Electricity
Light
+
heat
In this example HEAT is wasted and it is transferred to
the surroundings, becoming very difficult to use.
Describe the following energy changes and state the “waste”
energy or energies:
1) A vacuum cleaner
2) A TV
3) A dynamo/generator
Efficiency
07/07/2017
Efficiency is a measure of how much USEFUL energy you
get out of an object from the energy you put INTO it.
For example, consider a TV:
Electrical
Energy (200J)
Sound (40J)
Efficiency = Useful energy out
Energy in
x100%
Some examples of efficiency…
07/07/2017
1) 5000J of electrical energy are put into a
motor. The motor converts this into 100J of
movement energy. How efficient is it?
2) A laptop can convert 400J of electrical energy
into 240J of light and sound. What is its
efficiency? Where does the rest of the
energy go?
3) A steam engine is 50% efficient. If it delivers
20,000J of movement energy how much
chemical energy was put into it?
0.2 or
20%
0.6 or
60%
40KJ
07/07/2017
Energy Transfer (“Sankey”) diagrams
Consider a light bulb. Let’s say that the bulb runs on 100
watts (100 joules per second) and transfers 20 joules per
second into light and the rest into heat. Draw this as a
diagram:
“Input” energy
100 J/s
electrical
energy
“Output” energy
20 J/s
light energy
80 J/s heat
energy (given to
the surroundings)
Example questions
Consider a kettle:
2000 J/s
electrical
energy
Sound
energy
Wasted
heat
Heat to
water
1) Work out each energy value.
2) What is the kettle’s
efficiency?
07/07/2017
Consider a computer:
150 J/s
electrical
energy
10 J/s
wasted
sound
20 J/s
wasted
heat
Useful
light and
sound
1) How much energy is converted
into useful energy?
2) What is the computer’s
efficiency?
Reducing Energy Usage
How can we reduce
energy usage?
07/07/2017
07/07/2017
P3.2 How can Electricity be Generated?
Generators (dynamos)
07/07/2017
Electricity is convenient because it can be transmitted over
long distances and can be used in many ways. But how is it
generated? We need to use a “generator”:
Basically, a generator works by
spinning a magnet near a coil of
wire. That’s useful, but how do we
get this magnet to keep spinning?
07/07/2017
Using primary energy sources in power stations
1) A fuel is burned in the boiler
2) Water turns to steam and the steam drives a
turbine
3) The turbine turns a generator – if you want
more electricity you have to burn more fossil fuels
4) The output of the generator is connected to a
transformer
5) The steam is cooled down in a cooling tower and
reused
Efficiency of Power Stations
07/07/2017
Heat
100J
Boiler
85J
Heat
Heat
Turbine
35J
Kinetic
Heat
Generator
30J
Electrical
Nuclear power stations
07/07/2017
These work in a similar way to normal power stations:
The main difference is that the nuclear fuel is NOT
burnt. This means that they produce less pollution
but they do produce radioactive waste instead.
Radioactive Waste - Ionisation
07/07/2017
Radiation is dangerous because it “ionises” atoms – in other
words, it turns them into ions by “knocking off” electrons:
Alpha radiation is the most ionising (basically, because it’s the
biggest). Ionisation causes cells in living tissue to mutate,
usually causing cancer.
Radioactive Contamination
07/07/2017
Simply being “irradiated” by a radioactive material doesn’t
have to be dangerous – for example, we have background
radiation around us all the time. However, being
“contaminated” is far more dangerous. Consider the example
of Alexander Litvinenko who was poisoned with polonium-210:
Timeline of Events
Video of risks from polonium 210
07/07/2017
Other ways of generating electricity
Can we drive the turbine directly
without burning any fossil fuels? Here
are some examnples...
Wind Power
07/07/2017
Wave Power
07/07/2017
Hydroelectric Power
07/07/2017
The National Grid
07/07/2017
Electricity reaches our homes from power stations through
the National Grid:
Power station
Step up
transformer
Step down
transformer
Homes
If electricity companies transmitted electricity at 230 volts
through overhead power lines there would be too much energy
loss by the time electricity reaches our homes. To ensure this
doesn’t happen, electricity companies transmit electricity at
higher voltages instead.
07/07/2017
P3.3 Which Energy source should we use?
Which power station?
07/07/2017
Type of
power station
Commissioning costs
Running costs
(p per KWh)
Decommissioning costs
Life span
(years)
Coal
£650 million
4
£100 million
40-80
Oil
£700 million
12
£100 million
40-80
Gas
£800 million
6
£100 million
30-40
Nuclear
£2 billion
3
£500 million
30-40
1) Which power station is the most expensive to build and
why?
2) Give one advantage of coal power stations
3) Why is nuclear fuel cheaper than oil?
4) Overall, which power station is the most expensive?
07/07/2017
Matching supply and demand…
Hydroelectric power
station might “kick in” here
“Baseline” power stations
Solar Panels and Thermal Towers
07/07/2017
What are the
advantages and
disadvantages of solar
power?
07/07/2017
Using Solar Energy in remote places
Geothermal Energy
07/07/2017
Geothermal energy can be used in _______ areas such as
______. In a geothermal source cold water is pumped down
towards ____ _____. The water turns to steam and the
steam can be used to turn ______. In some areas the _____
rising at the surface can be captured and used directly.
Words – steam, Iceland, volcanic, turbines, hot rocks
Non-renewable energy sources
07/07/2017
Advantages
Disadvantages
Cheap fuel costs
Costs a lot of
money to
decommission a
nuclear plant
Good for “basic
demand”
Reliable
Coal, oil, gas and
nuclear
Fuel will run
out
Short start-up time for
gas and oil
Nuclear produces little
pollution
Pollution – CO2 leads to
global warming and SO2
leads to acid rain
Renewable energy sources summary
07/07/2017
Advantages
Disadvantages
Zero fuel costs
Unreliable
(except for
hydroelectric)
Don’t produce
pollution
Hydroelectric
is good for a
“sudden”
demand
Solar is good for
remote locations
(e.g. satellites)
Wind, tidal,
hydroelectric and solar
Expensive
to build
Tidal barrages destroy the
habitats of wading birds
and hydroelectric schemes
involve flooding farmland
Electricity Supply in the UK
07/07/2017
Notice that, due to all these advantages and disadvantages, we
use a variety of sources of energy in the UK: